US2668603A - Vibration damping device - Google Patents

Description

F 1954 w. R. WINSLOW VIBRATION DAMPING DEVICE Filed 001;. 15

FIG

S e W a V I" 1 MI INVENTOR WILLIAM WINSLOW ATTORNEY drical chamber 35 which is disposed within the piston head at right angles to the passage 23. A metering piston 35 is provided within cylindrical chamber 35, the reduced end 31 of the metering piston being adapted to extend into the passage 28 to constrict the opening thereof. A coiled spring 33 is'provided around the metering piston and abutting the shoulder 39 in the cylindrical chamber 35, this spring tending to normally keep the metering piston end 31 out of the passag 28.

A small axial drainage opening 40 in the piston 36 is provided to permit the passage of liquid from the chamber 35 to the passage 28.

A similar auxiliary or secondary passage through the piston head for the movement of liquid from chamber A to chamber B is provided in association with the passage 30, there being provided an inlet 4| on the face of the piston head 2| adjacent the chamber A through which the liquid passes against the ball 42 and its holding spring 43 into the cylindrical chamber 44 in which is disposed the metering piston 45, the reduced end 46 of which is adapted to at times extend into the passage 30 to constrict its opening, being normally held in the chamber 44 by the spring 48 against the shoulder 52. The metering piston 45 is provided with a small axial drainage opening 41 which is adapted to permit the passage of liquid from the inlet 4| to the passage 35.

The piston rod 24 outside the cylinder is connected either directly or indirectly to the element which is subjected to vibration so that longitudinal movement of the piston rod coincides with the movement of the vibrating or movable part of the airplane or other machine for which damping is desired. The cylinder may be supplied with hydraulic fluid through the filling hole 55 which is closed by the plug 5!.

Assuming that the piston head moves in the direction from B toward A, a greater pressure exists in the liquid in the chamber A than in the chamber B and therefore the liquid tends to pass through the piston to equalize the pressures. The principal flow of liquid is through the passage '28 and the check valve 29. No liquid flows through the passage 30 since this is prevented by the check valve 3|. Some liquid passes through the inlet 4| past the ball 42 which is lightly held by the spring 43 into the cylindrical chamber 44. This additional liquid in the chamber 44 exerts'a pressure on the metering piston 45 and moves it more or less into the passage 30 against the pres-.

sure of the spring 48. Some of the liquid in the cylindrical opening 44 escapes through the small axial drainage opening 41 into the passage 32. So long as there is a movement of liquid from chamber A to chamber B and enough differential pressure across the metering piston 45 to overcome the force of the spring 43, the metering piston 45 remains in the' displaced position extending into the passage 3!). When this differential pressure is insumcient to overcomethe spring force, the metering piston 45 moves back into the cylindrical chamber 44 leaving the passage 35 the corresponding parts 28, 29, 4|, 42, 44, 45, 45, 41, and 48.

However, if liquid in passing from chamber B to chamber A at a relatively rapid rate becomes reversed in its direction of flow due to a sudden change in the direction of the movement of the piston rod 20 and the piston head 2|, a correspondingly small amount of liquid, depending upon the time interval, will have escaped from the opening 44 through the drainage passage 41 and hence the metering piston 45 will have moved a correspondingly short distance back into a position of less restriction of the passage 30 and will therefore continue to be in a position to partly constrict the reverse flow of liquid through the opening 33. As the flow continues from chamber B to chamber A, the metering piston 45 moves out of the passage 30 as to allow less restricted flow through the orifice and check valve.

Since the damping effect is proportional to the restriction in the flow between the chambers A and B, damping occurs for a short period of time immediately after each sudden reversal in either direction. During this short period of time, the damping effect of the constriction varies inversely with the time and directly with some power approximately the square of the velocity of liquid flow.

While I have shown and particularly described the valve mechanism for controlling the flow of hydraulic liquid through the piston head, the valve mechanism may be as well installed outside the piston and cylinder in outside passageways hydraulically connecting the two working cham-.

bers.

An alternative form of my invention is shown in Figures 2 and 3 in which a valving arrangeber and the movement of the rotary piston 51 1 corresponds in its effect to the movement of the cylindrical piston head 2| of the form shown in Figure 1. The valve arrangement in the dam 55 consists of two passages 28A and 30A each having a spring-pressed ball check valve indicated respectively as 29A and 3|A. Passage 28A permits liquid to flow from the chamber A to the chamber B through the spring-pressed ball check 29A.

The other passage 30A permits the flow of hydraulic liquid from the chamber B to the cham-' ber A through the spring-pressed ball check valve 3|A. Hydraulic liquid may also pass from the chamber B to the chamber A through an auxiliary passageway having an inlet 32A which is on the' face of the dam 55 adjacent the chamber B, this inlet 32A being normally closed by the ball 33A held in place by the spring 34A. The inlet 32A is connected to a cylindrical chamber 35A which is disposed within the, dam 55 substantially at right angles to the passage 28A. A metering piston 36A is provided within the cylindrical cham ber 35A, the reduced end 31A of the metering piston being adapted to extend into the passage 28A to constrict the opening thereof. A coiled spring 38A is provided around the metering piston and abutting the shoulder 39A in the cylindrical chamber 35A, this spring tending to nor-' mally keep the metering piston end,31A out of the passage 28A. A small axial drainage opening 40A in the metering piston 36A is provided to a messa es sa u es mmhamber i 3i&---

lireigs th dam 5. th m r mam from; e i D end: 5%; t wh ch adante tt at t mes; extend,- ntathe a sa e; 3. a cosm c-t erO e i hamster-i.

The functioning of the;valvesmechanisms-as;

above described for the preferred form of the deviceshown in Figural; applies also to the alternative form of the rotary piston shown in Figures :2 and 3;,

The advantages of myjnventiomwill-be apparent from the above description'of the damping effect produced upon the reversal ofjthe' liquid n in either-direction: mygdampingu i vice when attached to-partsoffairplanes :andfthelikewhich are requiredto Ice-moved forircontrol; purposes by the pilot or 'operator does not-impose additional resistance to movements made for normal operating control, even successive movements in opposite direction when such movements are made in the normal manner. My device is effective in damping reversals of movement of frequencies above those of desired operator-control movements, and of the order of frequency of vibrations, shimmying, and oscillations encountered in airfoil surfaces, castered landing wheels, vehicle steering wheels and the like during operation thereof. The actual frequency which it may be desirable to damp out may be selected, and the damping device openings and spring pressures may be selected to effect the damping of frequencies which are undesired.

My device is relatively simple to manufacture and use, and requires no manitenance except that which is normally associated with hydraulic damping mechanisms. My device damps quick reversal movements such as vibrations without seriously increasing the resistance to normal movements in either direction.

I claim:

1. A vibration damping device comprising a closed hydraulic cylinder having a piston adapted to move therein defining left and right hydraulic working chambers; a left-to-right one-way conduit and right-to-left one-way conduit; variable constricting means for each of said one-way conduits; actuating means for each of said constricti'ng means including an hydraulic plunger and a cylindrical cavity in which said plunger moves, a check-valved inlet arranged to admit hydraulic liquid from the working chamber having the higher hydraulic pressure to the plunger cavity of said means which serves to constrict the flow in the conduit which carries liquid from the opposite chamber, a spring means for moving said plunger against the hydraulic pressure in said cavity when substantially no flow is being admitted through said check-valved inlet, and a means for bleeding the hydraulic liquid from said plunger cavity to the working chamber of lower pressure.

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- lower-pressure;

3;; A; vibration. dam-pings-devicezacornprisings ar closed hydraulic cylindenihaving;airfixedzradiaii; partition.v and a; rotary pistom'adapted toamovsa therein defining left; andiirigh-tihydraulim works. zchambers; ,saidimovableipistom beingzattachedr to; zar-shaftgi leftrto rightl and: night-tadcftr once. W y; conduits: in: said: fixed"; partitioni adapted; ma: carry liquid between said chambers; plug means extending into each of said one-way conduits and adapted to more or less constrict the flow of hydraulic liquid therethrough; an hydraulic plunger for actuating each of said plug means including a cylindrical cavity in said fixed partition in which said plunger moves; a check-valved inlet to each cylindrical cavity, one arranged to admit hydraulic liquid from said right working chamber to the cavity and corresponding plug means in said left-to-right one-way conduit and the other arranged to admit hydraulic liquid from said left working chamber to the cavity and corresponding plug means in said right-to-left oneway conduit; spring means at each plug for moving said plunger against the hydraulic pressure in said cavity when substantially no flow is being admitted through said corresponding checkvalved inlet; and means for bleeding the hydraulic liquid from said plunger cavity to the working chamber of lower pressure.

4. A vibration damping device comprising hydraulic cylinder and piston elements arranged to provide left and right working chambers, left-toright and right-to-left, one-way pressure relief conduits arranged to pass liquid from one working chamber to the other on piston movements in opposite directions, a variable flow reducing valve in each of said one-way conduits, pressure actuated devices for operating said flow reducing valves in the flow reducing direction, means for returning said flow reducing valves in the opposite direction, a one-way pressure transmitting passage extending from the left working chamber to the pressure actuated device controlling the right-to-left conduit, a one-way pressure transmitting passage from the right working chamber to the pressure actuated device controlling the left-to-right conduit, a bleed passage for releasing liquid trapped in the passage from the left working chamber back into the right-to-left pressure relief conduit and a bleed passage for releasing liquid trapped in the passage from the right working'chamber back to the one-way, leftto-right pressure relief conduit.

5. A vibration damping device comprising a hydraulic cylinder and piston combination with left and right working chambers, left-to-right and right-to-left one-way conduits adapted to carry liquid from one working chamber to the other as said piston moves in the opposite direction respectively, variable constricting means for each of said one-way conduits, storage chambers in which each of said variable constricting means moves, a check-valved passage allowing liquid to pass only from said right chamber to the storage chamber and constricting means for said left-toright conduit, a check-valved passage allowing liquid to pass only from said left chamber to the storage chamber and constricting means for said right-to-left conduit, said constricting means in said lft-torlight conduit moving from an initial configuration having a certain constricted area of passage to a configuration having a varied constricted area when there is a substantial flow of liquid through said right-to-left conduit, and said constricting means in said right-to-left conduit moving from an initial configuration having a certain constricted area of passage to a configuration having a varied constricted area when there is a substantial flow of liquid through said left-to-right conduit, and means to return each of said variable constricting means to said initial configuration when the flow in the corresponding check-valved passage is slight or non-existent.

a hydraulic cylinder and pistoncombination providing left and right working chambers, left-toright and right-to-left one-way conduits to pass liquid from one working chamber to the other on piston movement in opposite directions, variable constricting means for controlling flow through each of said one-way conduits, pressure actuated devices for operating said constricting means, a one-way pressure transmitting passageextending from the left working chamber to the pressure actuated device controlling the right-to-left conduit, a one-way pressure transmitting passage from the right working chamber to the pressure actuated device controlling the left-to-right conduit, means for restoring said pressure actuated devices to a normal conduit open position upon release of pressure on said devices and bleed passages for releasing liquid trapped in the one-way passages to said devices.

WILLIAM R. WINSLOW.

References Cited in the file of this patent UNITED STATES PATENTS

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